Buchanan R L, Edelson S G, Snipes K, Boyd G
Food Safety Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, Pennsylvania 19038, USA.
Appl Environ Microbiol. 1998 Nov;64(11):4533-5. doi: 10.1128/AEM.64.11.4533-4535.1998.
Three strains (932, Ent-C9490, and SEA13B88) of Escherichia coli O157:H7 were used to determine the effectiveness of low-dose gamma irradiation for eliminating E. coli O157:H7 from apple juice or cider and to characterize the effect of inducing pH-dependent, stationary-phase acid resistance on radiation resistance. The strains were grown in tryptic soy broth with or without 1% dextrose for 18 h to produce cells that were or were not induced to pH-dependent stationary-phase acid resistance. The bacteria were then transferred to clarified apple juice and irradiated at 2 degrees C with a cesium-137 irradiator. Non-acid-adapted cells had radiation D values (radiation doses needed to decrease a microbial population by 90%) ranging from 0.12 to 0.21 kGy. D values increased to 0.22 to 0.31 kGy for acid-adapted cells. When acid-adapted SEA13B88 cells were tested in five apple juice brands having different levels of suspended solids (absorbances ranging from 0.04 to 2.01 at 550 nm), radiation resistance increased with increasing levels of suspended solids, with D values ranging from 0.26 to 0.35 kGy. Based on these results, a dose of 1.8 kGy should be sufficient to achieve the 5D inactivation of E. coli recommended by the National Advisory Committee for Microbiological Criteria for Foods.
使用三株大肠杆菌O157:H7（932、Ent-C9490和SEA13B88）来确定低剂量伽马辐射消除苹果汁或苹果酒中大肠杆菌O157:H7的有效性，并表征诱导pH依赖性稳定期耐酸性对辐射抗性的影响。这些菌株在含有或不含1%葡萄糖的胰蛋白胨大豆肉汤中培养18小时，以产生诱导或未诱导出pH依赖性稳定期耐酸性的细胞。然后将这些细菌转移至澄清的苹果汁中，并在2摄氏度下用铯-137辐照器进行辐照。未适应酸性环境的细胞的辐射D值（使微生物数量减少90%所需的辐射剂量）范围为0.12至0.21千戈瑞。适应酸性环境的细胞的D值增加到0.22至0.31千戈瑞。当在五个悬浮固体含量不同（550纳米处吸光度范围为0.04至2.01）的苹果汁品牌中测试适应酸性环境的SEA13B88细胞时，辐射抗性随悬浮固体含量的增加而增加，D值范围为0.26至0.35千戈瑞。基于这些结果，1.8千戈瑞的剂量应足以实现食品微生物标准国家咨询委员会推荐的大肠杆菌5D级灭活。
